This application claims the priority benefit of Taiwan application serial no. 89121896, filed Oct. 19, 2000.
1. Field of Invention
The present invention relates to a projection device. More particularly, the present invention relates to a fastening device for a projector lamp that requires a single spring only.
2. Description of Related Art
Projector is a common office and household device. Using a projector, a small picture can be put on a relatively large screen for several people to look at all at once. For example, a lecturer can project some of the information related to the speech to a big screen for every participants of the lecture to read. With the rapid progress in electronic technologies, projector not only can project simple image but electronic images can also be projected onto a wall.
However, no matter what type of projector is used, images are generated by a projector lamp. Hence, images and projector lamp have a close and sensitive relationship with each other. If the direction of lamp projection is not on the pre-determined optical axis, brightness and color texture of the image on the projection will be affected. Therefore, fastening the lamp onto a lamp casing such that there is minimal deviation from the optical axis is an important factor for producing a quality image.
Conventionally, to prevent deviation of lamp projection direction, a plurality of springs is required in relation with the lamp casing. These springs are usually difficult to assemble. FIG. 1 is a perspective view looking from the bottom of a conventional structure for fastening the projector lamp to a lamp casing before a spring is positioned in the final position. FIG. 2 is a perspective view looking from the bottom of a conventional structure for fastening the projector lamp to a lamp casing after a spring is positioned in the final position. FIG. 3 is a perspective view looking from the top of a conventional structure for fastening the projector lamp to a lamp casing after a spring is positioned in the final position.
A lamp casing 100 is shown in FIGS. 1 to 3. The lamp casing 100 has a central space enclosed by four sidewalls so that a lamp 101 can mount inside the casing 100. In FIG. 1, only the left sidewall and the lower sidewall of the lamp casing can be seen. After the lamp 101 is positioned inside the lamp casing 100, a strip-shaped spring 102 and a sheet-shaped spring 110 (see FIG. 2) are used for fastening the lamp 101 in a designed positioned. Ultimately, the projection direction of the lamp 101 and the designed optical axis will coincide. As shown in FIG. 1, the left sidewall has a first opening 104, a second opening 106 and a third opening 108. The spring 102 must first penetrate the second opening 106 so that one end is fixed upon another opening 107 (see FIG. 3). The other end of the spring 102 is fixed upon the opening 104. After fixing the spring 102 on the destined openings 104, 106 and 107, stress created by deformation will fasten the lamp 101 onto the fours sidewalls of the lamp casing 100. The structure formed by the combination of the lamp 101 and the lamp casing 100 has a rectangular design. The lamp wall is constructed using non-explosive glass.
Besides the strip-shaped spring 102, the sheet-shaped spring 110 is also required. In FIG. 2, the sheet-shaped spring 110 is mounted through the opening 108. The lamp 101 is installed by pushing from one corner of the lamp to the other corner of the lamp wall. Hence, the lamp 101 has at least three corners fixed by the sheet spring 110 and the strip spring 102.
The aforementioned conventional method of fixing the lamp must rely on two or more springs. In particular, the strip spring 102 must pass through the openings 106 and 107. Hence, the step of assembling the lamp and the lamp casing together is difficult.
Accordingly, one object of the present invention is to provide a fastening device for projector lamp. The fastening device includes a lamp, a lamp casing and a strip-shaped spring that fastens the lamp onto the lamp casing. The lamp casing has a first sidewall, a second sidewall, a bottom wall and an upper connective structure, together they encloses a central space. The first sidewall has a first opening and the second sidewall has a hook groove. There is a second opening between the second sidewall and the bottom wall. The spring has a first end and a second end. A central portion of the strip-shaped spring can be latched by the hook groove. The first end of the spring is fixed by the first opening on the first sidewall. The second end of the spring has an internal recess structure. The second end of the spring passes through the second opening and fastens onto a recess groove on the lamp. The deform stress produced by passing the spring through the first opening, the hook groove and the recess groove is capable fixing the lamp relative to the lamp casing.
According to the invention, the hook groove is open-ended and hence the stripshaped spring can easily slip into position. Consequently, the assembly process is greatly simplified. In addition, the internal recess structure at the second end of the strip-shaped spring can combine with the recess groove on the lamp to fix the lamp, thereby eliminating the need for a conventional sheet-shaped spring. Since only a single spring is required in this invention, the fastening structure and the assembly process can both be simplified.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.